1. Field of the Invention
This invention relates to a method for improving the absorbency characteristics of cellulosic fibers, and more particularly to such a method which is useful in the preparation of absorbent materials for catamenial tampons, sanitary napkins, and other absorbent dressings.
2. Description of the Prior Art
Various techniques have been described in the literature for increasing the absorbency of cellulosic materials. Such techniques include, for example, the preparation of alloy fibers having matrices of regenerated cellulose and, uniformly dispersed therein, polyacrylates (e.g., Smith U.S. Pat. No. 3,884,287), acrylate/methacrylate copolymers (e.g., Allen et al U..S. Pat. No. 4,066,584; Meierhoefer U.S. Pat. No. 4,104,214; and Allen U.S. Pat. No. 4,240,937), alkylene vinyl ether/ethylene dicarboxylic acid copolymers (e.g., Denning U.S. Pat. No. 4,165,743), sulfonic acids (e.g., Allen U.S. Pat. No. 4,242,242, polyvinylpyrrolidone (e.g., Smith U.S. Pat. No. 4,136,697), cellulose sulfate (e.g., Smith U.S. Pat. No. 4,273,118), carboxymethylcellulose (e.g., Smith U. S. Pat. No. 4,289,824), or the like.
Viscose rayon or other regenerated cellulose polymer alloy fibers may be subjected during preparation to one or more hot, aqueous baths. For example, post-regeneration treatments in hot water baths at temperatures of from ambient (20.degree.-25.degree. C.) to as much as 100.degree. C. have been described in various of the above patents. Such treatments have not, however, been disclosed as having any appreciable effects on the absorbency characteristics of the cellulosic materials.
Other treatments of cellulosic fibrous materials have been proposed in the literature for increasing their absorbency. Thus, the treatment of carboxymethylcellulose fibers in hot aqueous baths containing cross-linking agents has been proposed to effect wet cross-linking of the fibers, with consequent increase in the absorbency thereof (see, for example, Steiger U.S. Pat. No. 3,241,553; Ells U.S. Pat. No. 3,618,607; and Chatterjee U.S. Pat. No. 3,971,379). None of this literature, however, suggests the use of hot water treatments per se for improving the absorbency of the cellulosic materials thereof.